Background: Chronic kidney disease (CKD) and hypertension are global public health problems associated with considerable morbidity, premature mortality and attendant healthcare costs. Previous studies have highlighted that non-invasive examination of the retinal microcirculation can detect microvascular pathology that is associated with systemic disorders of the circulatory system such as hypertension. We examined the associations between retinal vessel caliber (RVC) and fractal dimension (DF), with both hypertension and CKD in elderly Irish nuns.

Conclusions: Individuals with hypertension have significantly narrower retinal arterioles which may afford an earlier opportunity for tailored prevention and treatment options to optimize the structure and function of the microvasculature, providing additional clinical utility. No significant associations between retinal vascular parameters and CKD were detected.

pone.0136434.g002: Retinal vascular fractal dimension measurement.The upper image illustrates a retinal fundus image and skeletonized line tracing of an eye with a low fractal dimension and less complex (more rarefied) branching pattern; the lower retinal fundus image and skeletonized line tracing illustrates a higher fractal dimension and a more complex (dense) branching pattern.

Mentions:
Fractal analysis was performed using digital retinal images centered on the optic disc. A single blinded trained grader (AMG) used a computer-based program [SIVA-FA, software version 1.0, School of Computing, National University Singapore] for measurement of fractal dimensions (DF) according to a standardized protocol [50]. Briefly, the optic disc was automatically detected by the software which identified the edges of the optic nerve head. The fractal dimension of the retinal vasculature was calculated within a predefined circular area from 0.5 to 2 disc diameters (Ddisc) away from the optic disc margin (Fig 2). The software performs automated skeletonized vessel tracing that does not differentiate between the arterioles and venules. Artefacts generated from choroidal vessels, peripapillary atrophy, pigmentary abnormalities and reflection from the nerve fibre layer were identified and manually erased. The software computed a DF from the refined skeletonized vessel tracing using the box-counting method which involves drawing predetermined size boxes which overlay the structures of interest calculating a fractal value [51]. These values represent a “global” summary measure of the whole branching pattern of the retinal vascular tree with larger values indicative of a more complex branching pattern [52].

pone.0136434.g002: Retinal vascular fractal dimension measurement.The upper image illustrates a retinal fundus image and skeletonized line tracing of an eye with a low fractal dimension and less complex (more rarefied) branching pattern; the lower retinal fundus image and skeletonized line tracing illustrates a higher fractal dimension and a more complex (dense) branching pattern.

Mentions:
Fractal analysis was performed using digital retinal images centered on the optic disc. A single blinded trained grader (AMG) used a computer-based program [SIVA-FA, software version 1.0, School of Computing, National University Singapore] for measurement of fractal dimensions (DF) according to a standardized protocol [50]. Briefly, the optic disc was automatically detected by the software which identified the edges of the optic nerve head. The fractal dimension of the retinal vasculature was calculated within a predefined circular area from 0.5 to 2 disc diameters (Ddisc) away from the optic disc margin (Fig 2). The software performs automated skeletonized vessel tracing that does not differentiate between the arterioles and venules. Artefacts generated from choroidal vessels, peripapillary atrophy, pigmentary abnormalities and reflection from the nerve fibre layer were identified and manually erased. The software computed a DF from the refined skeletonized vessel tracing using the box-counting method which involves drawing predetermined size boxes which overlay the structures of interest calculating a fractal value [51]. These values represent a “global” summary measure of the whole branching pattern of the retinal vascular tree with larger values indicative of a more complex branching pattern [52].

Background: Chronic kidney disease (CKD) and hypertension are global public health problems associated with considerable morbidity, premature mortality and attendant healthcare costs. Previous studies have highlighted that non-invasive examination of the retinal microcirculation can detect microvascular pathology that is associated with systemic disorders of the circulatory system such as hypertension. We examined the associations between retinal vessel caliber (RVC) and fractal dimension (DF), with both hypertension and CKD in elderly Irish nuns.

Conclusions: Individuals with hypertension have significantly narrower retinal arterioles which may afford an earlier opportunity for tailored prevention and treatment options to optimize the structure and function of the microvasculature, providing additional clinical utility. No significant associations between retinal vascular parameters and CKD were detected.